A so-called video format signal is similar to that of a composite video signal. More particularly, a video format signal includes successive field signals each of which has an information signal portion for carrying video information, and a synchronizing signal portion which includes horizontal and vertical blanking intervals. In general, each frame of the video format signal includes a pair of field signals.
In prior art methods of recording a video format signal on a recording medium (e.g. a disk), a time code is generated which represents an elapsed time of the video format signal. The time code is inserted in the vertical blanking interval of the format signal, thereby facilitating the location of a specified portion (e.g. frame) of the signal. In recording a video format signal, for example, a composite video signal of an NTSC system having a frequency of 59.94 Hz. a problem occurs in that the period of thirty (30) frames does not exactly correspond to one (1) second. As a result, there has been employed a recording method in which a time code is generated such that the period of thirty (30) frames of the video format signal will correspond to one (1) second, and the generated time code is inserted in the vertical blanking interval of the video format signal.
Such a time code has the advantage of not requiring arithmetic operations, thereby allowing the time code to be generated by a simple circuit arrangement. However, a problem still occurs in such methods since the time difference between the real elapsed time and the time represented by the generated time code is about 60 ms/min, which corresponds to about 3.6 secs/hr. Accordingly, in the operation of such a method, the specified location of the video format signal cannot be accurately found due to this time difference. Referring to FIGS. 1(A) and 1(B), wherein FIG. 1(A) shows frames of the video format signal according to the prior art method in which the period of thirty (30) frames is regarded as one second, and FIG. 1(B) shows frames of a video format signal of the NTSC system. As shown in FIG. (1B), thirty (30) frames of the video format signal correspond to about 1.001 seconds which converts into a time difference between the periods indicated in FIGS. 1(A) and l(B) of about 3.6 secs/hr.
Thus, there is a continuing need in the art for recording a video format signal in which the time difference or error between a generated time code and the real elapsed time of the video format signal is relatively small.